1. Field of the Invention
The present invention relates to a semiconductor device comprising a semiconductor substrate having circuit elements formed therein and a protective film formed on the semiconductor substrate. The present invention also relates to a manufacturing method of this type of semiconductor device.
2. Description of the Related Art
A semiconductor device generally comprises a semiconductor substrate having circuit elements that are formed within the semiconductor substrate. Generally, a protective film is formed on the semiconductor substrate in order to insulate and/or protect the circuit elements from the external environment. Typically, imide resin such as polyimide is used to form an organic protective film. On the other hand, silicon oxide, silicon nitride, silicon oxynitride, phosphorus glass, and the like are used to form an inorganic protective film. The material to form the protective film varies depending on usage of the semiconductor device.
It is known that electrical charges accumulate on the surface of and/or within the protective film during a manufacturing process, a packaging process, a shipping process and/or a using process of the semiconductor device. This phenomenon is due to a number of causes. For example, contact with cutting water during dicing process causes electrical charges to accumulate on the surface of and/or within the protective film. An exposure to dry air during a solder reflow process causes electrical charges to accumulate on the surface of and/or within the protective film. Further, friction with paper during the shipping process causes electrical charges to accumulate on the surface of and/or within the protective film. The above-mentioned reasons cause negative charges to accumulate on the surface of and/or within the protective film. When negative charges accumulate on the surface of and/or within the protective film, positive charges that are attracted by the negative charges accumulate in the surface portion of the semiconductor substrate. This phenomenon disrupts the balance of electrical charges within the semiconductor substrate, thereby creating problems such as lowering the breakdown voltage of the circuit elements formed within the semiconductor substrate.
Japanese Laid-Open Patent Publication No. 1995-153921 discloses a technique for forming a conductive layer within the protective film in order to discharge negative charges that accumulate within the protective film.